EFFECT OF PASSAGE OF ELECTRIC CURRENT ON THE COEFFICIENT OF FRICTION OF THIN FILMS OF AMORPHOUS CARBON (a-C) DOPED WITH Ni AND Cu.

• Grant number: 25/14524-9
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: September 01, 2025
• End date: August 31, 2027
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Principal Investigator: Andre Paulo Tschiptschin
• Grantee: Lázaro Aleixo dos Santos
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 19/18572-7 - New carbon materials: their relevant space, environmental and relevant spin off applications, AP.TEM

Abstract

This proposal aims to further study diamond-like carbon (DLC) coatings obtained by physical vapor deposition (PVD), with a focus on doping these coatings with metals such as nickel (Ni) and copper (Cu). These materials exhibit high hardness, low roughness, wear resistance, and excellent tribological performance, especially under critical friction conditions. Recent studies indicate that metal doping can significantly modify the structural and conductive properties of films, influencing their performance in tribological applications, including those under electric fields - a phenomenon known as electrified tribology. The research proposes deposition of pure DLC, Ni-doped DLC (DLC:Ni), and Cu-doped DLC (DLC:Cu) on glass, silicon, and H13 steel substrates using the pDCMS (Pulsed-DC Magnetron Sputtering) technique in a reactor at LABPLASMA (USP Plasma Surface Treatment Laboratory). For DLC (a-C) films, a Si interlayer will be deposited. The primary objective of doping these coatings with the aforementioned metallic elements is to investigate how film formation occurs upon doping, how the surface conductive properties vary, and their impact on the coefficient of friction in electrified tribological tests. The proposal integrates and expands the group's previous advances in carbon films obtained using CVD and PVD techniques, including projects with DLCs, graphenes, dichalcogenide-based coatings, as well as plasma and laser surface modification. The coatings studied here have high potential for application in various sectors, including transportation, electric vehicle propulsion systems, and wind turbines. Microstructural and compositional characterization will be performed by FEG-SEM, TEM, FIB, and Raman spectroscopy, allowing us to evaluate the influence of dopants on the nanometric organization of the films, the sp²/sp³ bond ratio, and the degree of graphitization before and after tribological tests. The mechanical properties of hardness and modulus of elasticity will be obtained by nanoindentation. Tribological tests will be performed using a reciprocating ball-on-plane tribometer. The tribometer will be electrified using a DC power supply with poles connected to both the sample and the counterbody, reversing the polarity in each test. Varying the polarity and current intensity will allow investigating the effects of electrification on the friction and wear of DLÇ and doped DLÇ films. The aim is to elucidate mechanisms still poorly understood in the literature, such as the formation of crystalline structures induced by shear or electric current, which are responsible for superlubricity regimes. The proposal combines fundamental nanoscale analysis with functional performance evaluation, aiming to establish correlations between structure, doping, and electrified tribological behavior. The expected results could contribute to reducing the friction coefficient of electric motors in motor vehicles, wind generators, and motor-generator sets responsible for generating electrical energy, increasing energy efficiency and sustainability in different industrial sectors. (AU)